Manufacture of lithographic stone artificially.



TTE STAT ALTENT orricn.

THOMAS MATIIIESON TI-IOM, OF WOODLANDS, HUGSII UNT, ENGLAND, ASSIGNOR TOTHE BRIT- ISH STONE AND MARBLE COMPANY LIMITED, OF LONDON, ENGLAND, ACORPORATION OF GREAT BRITAIN.

MANUFACTURE OF LITHOGRAPHIC STONE ARTIFIGIALLY.

To all whom 'it may concern:

Be it known that I, THOMAS bIA'lHIIGSON Tnoai', a subject of the King ofGreat Britain, and resident of Voodlands, Cheshunt, in the county ofI'Iertiord, England, lithographer, have invented new and. usefulImprovements in the lvIaiuifacture of Lithographic Stone Artificially,of which the tollowing is a specification.

Lithographic stones such as are usually employed for printing arenatural products derived from certain special quarries and when largeand of good quality are very expensive. It has been proposed to makelitho graphic stones artilicially by taking the waste chips and debrisfrom the quarries and stone yards, where such stones are hewn andgrinding up the same into line powder, mixing the same with lime,slaking the mixture and molding it into slabs which when dry, arehardened by means of carbonic acid gas. These reconstructedlithographic. stones, when properly made are found admirable. I have nowdiscovered that excellent lithographic stones can be made from the wastematerial known as slag in a somewhat similar way, with or without theaddi tion of natural stone. This material (slag) has already been groundup and used in making cement, tiles, bricks and as an ingredient in avariety of articles which contain slaked lime and are hardened by carbondioxid, but has not been used in the manufacture of lithographic stone,the properties of which are peculiar and have not hitherto beensatisfactorily reproduced or imitated except by the reconstruction oithe debris of the natural stone as above mentioned.

In manufacturing lithographic stone according to my present invention Itake blast furnace or granulated slag and reduce the same to a conditionof powder, by means of any suitable grinding apparatus. The pow deredslag is mixed with a suitable proportion of lime and the mixture isslaked with Water. While in a plastic state the mixture of slag powderand lime is molded in dies under considerable compression into slabs ofSpecification of Letters Patent.

Application filed June 12, 1908.

Patented July 13, 1909.

Serial No. 438,206.

a suitable size and tlllclfllOSS to form lithographic stones. \Vlientaken from the dies the slabs are dried and introduced into closedvessels into which carbonic acid gas is admitted or forced graduallyuntil the lime is converted into carbonate and will absorb no more gas.Slabs thus produced "from slag it'ultil every requirement oflithographic stones and in many respects they are superior to thenatural article.

I may remark that to the ground slag may be added powdered naturalstone, dolomite, silica, alumina, or marble obtained from the quarriesor yards if desired.

The carbonatin g of the slabs may be etllected by any of the knownmethods, by means of which the thorough iinluration ot' the same isinsured, for instance, the slabs having been molded and dried and placedin a closed .'essel, the air is exhausted from the latter and carbonicacid gas is allowed to enter. The carbonic acid gas is graduallyabsorbed by the slabs and fresh gas is from time to time supplied butfor a time not in sullicient quantity to reach atmospheric pressure,subsequently however for completing the carbonation actual pressure isnecessary which will rary according to the thickness and density of thestone. For the largest stones used, pressure amounting to some 300-l00lbs. to the square inch may be required.

What I claim as my invention and desire to secure by Letters Patent, is:

The process of maniiitacturing lithographic slone consisting inpowdering slag, mixing it with lime, molding the mixture into slabs andsubmitting the molded slabs to the action of carbonic acid gas graduallyadmitted thereto until the entire mass is hardened.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

THOMAS HATHIESON TIIOM.

l/Vitnesses U. J. TILMAN, A. S. BISHOP.

